Treatment of montan wax with chromic acid and simultaneous formation of chromic tanning mash



P A 2,971,813 Patented Feb 14, 19.61

TREATMENT OF MONTAN WAX WITH CHROMIC ACID AND SIMULTANEOUS FORMATION OF CHROMIC TANNING MASH Antoni Sentek, Swierczewskiego-street 149, m.104, Warsaw, Poland No Drawing. Filed Oct. 4, 1957, Ser. No. 688,140

Claims priority, application Poland Oct. 16, 1956 5 Claims. (Cl. 8-94.26)

Among the known methods of improving montan wax, the method leading to most valuable products is that which consists in treating the wax at an elevated temperature with a mixture of sulphuric acid and chromic acid or sodium bichromate or patassium bichromate and -in combining subsequently the fatty acids obtained in the oxidized wax, with, dependently on the desired properties of the final products, alcohols or amines, eventually with the partial conversion of the fatty acids into salts of the alkali metal or earth alkali metal group.

The use of chromic acid or of bichromates for the oxidation of wax exhibits the great advantage that the oxidized product obtains, without losing the hardness characterizing montan wax, besides the light colour, a high acid number which is of essential importance when further working the wax.

The disadvantage of this method consists in that a relatively great quantity of compounds of the six valent chrome must be used e.g. to one part of montan wax about 3.5 parts of sodium bichromate are used.

It is true, that according to known methods the waste compounds of the trivalent chrome are in known manners reoxidized to the compounds of the six valent chrome, but such an oxidation is expensive and connected with considerable chrome losses.

The method of obtaining a chrome mash for tanning to leather, in which for reducing the six valent chrome compounds and for introducing the required substances into the mash, bituminous substances are used, is also known. When applying this method, as bituminous substances are used, among others, waxes e.g. montan waxes, one part of said bituminous substance passing into the mash, while the remaining part oxidizes to the improved waxes. This proceeding is described in the Polish Patent No. 33,690 and constitutes a very advantageous solution of a cheap parallel production of improved waxes especially 'for the reason that the obtained mash exhibits better tanning properties than mashes normally prepared in tanneries. The demand for improved waxes being very brisk, the quantities of the obtained mash may, however, be, for contrivance reasons, too considerable and burdensome to the wax-producer, whereby the problem of reducing the proportional quantity of tanning mash and the use of bichromate remained actual also in this case.

Trials have been made for solving this problem by preliminarily treating the wax with nitric acid, the results were however unsatisfactory. On treating the wax with nitric acid having a concentration of above 30,% and oxidizing the same subsequently with a dim nished quantity of bichromate, soft and mucilaginous products were obtained.

On treating preliminarily disresined wax with nitric acid having a concentration of below 30%, after its subsequent oxidation by means of a diminished quantity of bichromate, light-coloured and hard wax was obtained, but the time of the preliminary treatment of the wax with nitric acid was too long and took 6-10 hours at a temperature of 95-100 C.

In the proceeding according to the present invention, the quantity of bichromate which is required for a suitable oxidation of the wax, is decreased up to about one third, a light-coloured, almost white product of a great hardness and of a high acid number being obtained, said number qualifying the same, after the wax has been submitted to esterification, as a wax of the highest quality.

The proceeding according to the present invention consists in that disresined or not disresined wax is preliminarily treated with nitric acid of a concentration of 46-50%, at a temperature not exceedng C. and no longer than one hour. This preliminary treatment of the wax with nitric acid is most advantageously achieved according to the method of bleaching wax as stated in the Polish. Patent No. 39,139, in which the nitric acid is caused to act upon the wax suspended therein, the wax having previously been crumbled so that the reaction revealing itself by the increase of the temperature, takesplace spontaneously without any supply of heat from. without. Keeping the temperature without exceeding 80 is obtained according to the invention, by suitably choosing, dependently on the quantity and on thequality of the montan wax, the concentration of the nitric acid within the above mentioned limits of 40-50%.

The preliminary treatment of the wax with nitric acid .is interrupted latest after an hour by pouring cold water on the mixture. Subsequently the wax is cleansed with water and thereupon it is oxidized by means of bichromate or chromic acid, without having been previously dried, 1 kg. of sodium bichromate being used to 1 kg. of montan wax of the start.

Owing to its bituminous origin, the montan wax preliminarily treated with nitric acid is oxidized most advantageously as stated in the Polish Patent No. 33,690 according to which, in addition to improved wax, chromic mash for tanning leather is obtained. The quantity of the obtained mash is in this case not so great when compared with the quantity of the obtained improved wax.

The difiiculties connected with the transport of the liquid mash and the inconveniences arising in consequence of the necessity of producing a standard mash of a constant specific weight are overcome according to the invention by the fact that the liquid mash is converted into a powdery dry substance by intensively spraying the liquid mash in a drying chamber through which heated air-is simultaneously passed. One obtains a product which is well soluble in water, is easily transportable and which admits the preparation of mashes of any desired concentration.

I claim:

1. A method for improving montan wax comprising the steps of dispersing montan wax in an aqueous solution of nitric acid having a concentration of about be- 7 tween 10-50%, so as to cause an exothermic reaction be tween said montan wax and said aqueous nitric acid, thereby raising the temperature of the thus formed reaction mixture; allowing said mixture to react for a period up to one hour while preventing the temperature thereof from rising above about 80 C.; coo ing said reaction mixture so as to substantially terminate said reaction; separating the thus treated montan wax from the remainder of said reaction mixture; and subjecting said separated montan wax to the action of an oxidizing agent selected from the group consisting of chromic acid and bichromates.

2. A method for improving montan wax comprising the steps of dispersing montan wax in an aqueous solution of nitric acid having a concentration of about between 40-50%, so as to cause an exothermic reaction between said montan wax and said aqueous nitric acid, thereby raising the temperature of the thus formed 16- action mixture; allowing said mixture to react for a period of about one hour while preventing the tempera- "ture thereof from rising above about 80 C.; thereafter introducing cold water into said reaction mixture so as to cool the same sutficieutly to substantially terminate said reaction; separating the thus treated montan wax fromthe remainder of said reaction mixture; and subjecting said separated montanwax to the action of an oxidizing agent selected from the group consisting of chromic acid and bichromates.

3. A method for improving montan wax comprising 'the steps of dispersing montan wax in an aqueous soluducing cold water into said reaction mixture so as to cool the same'sufiiciently to substantially terminate said reaction; separating the thus treated montan wax from the remainder of said "reaction mixture; washing said separated montan wax with water so as to remove residual "aqueous nitric acid'therefrom; and subjecting said sepa rated and washed montan wax to the action of an aqueous solution of an oxidizing agent selected from the group consisting of chromic acid and bichromates.

4. Amethod for improving montan wax comprising the steps of dispersing montan wax in an aqueous solution of nitric acid having a concentration of about between 40-50%, so as to cause an exothermic reaction between said montan wax and said aqueous nitric acid, thereby raising the temperature of the thus formed reaction mixture; allowing said mixture to react for a period up to one hour while preventing the temperature thereof from rising above 80 C.; cooling said reaction mixture .4 so as to substantia ly terminate said reaction; separating the thus treated montan wax from the remainder ot said reaction mixture; subjecting said separated montan wax to the action of an oxidizing agent selected from the group consisting of chromic acid and bichromates, so as to improve the quality of said montan wax and simultaneously to form a chromic tanningmash; and separating the thus treated'montan wax from said tanning mash.

5. A method for improving montan wax comprising the steps of dispersing montan wax in an aqueous solution of nitric acid having a concentration of about between 4050%, so as to cause an exothermic reaction between said montan wax and said aqueous nitric acid, thereby raising the temperature of the thus formed reaction mixture; allowing said mixture to react for a period up to one hour while preventing the temperature thereof from rising above about C.; cooling said reaction mixture so as to substantially terminate said reaction; separating the thus treated montan wax from the remainder of said reaction mixture; subjecting said separated montan wax to the action of an oxidizing agent selected from the group consisting of chromic acid and bichromates, so as to improve the quality of said montan wax and simultaneously to form a chromic tanning mash; separating the thus treated montan wax from said tanning mash; and spray drying the thus separated tanning mash so as to transform the same into a powdery dry substance.

References Cited in the file of this patent UNITED STATES PATENTS 1,092,629 Barmstedt Apr. 7, 1 914 FOREIGN PATENTS 33,690 Poland Feb. 15, 1950 39,139 Poland Apr. 30, 1956 305,552 Great Britain Feb. 5, 19 29 

5. A METHOD FOR IMPROVING MONTAN WAX COMPRISING THE STEPS OF DISPERSING MONTAN WAX IN AN AQUEOUS SOLUTION OF NITRIC ACID HAVING A CONCENTRATION OF ABOUT BETWEEN 40-50%, SO AS TO CAUSE AN EXOTHERMIC REACTION BETWEEN SAID MONTAN WAX AND SAID AQUEOUS NITRIC ACID, THEREBY RAISING THE TEMPERATURE OF THE THUS FORMED REACTION MIXTURE; ALLOWING SAID MIXTURE TO REACT FROM A PERIOD UP TO ONE HOUR WHILE PREVENTING THE TEMPERATURE THEREOF FROM RISING ABOVE ABOUT 80*C.; COOLING SAID REACTION MIXTURE SO AS TO SUBSTANTIALLY TERMINATE SAID REACTION; SEPARATING THE THUS TREATED MONTAN WAX FROM THE REMAINDER OF SAID REACTION MIXTURE; SUBJECTING SAID SEPARATED MONTAN WAX TO THE ACTION OF AN OXIDIZING AGENT SELECTED FROM THE GROUP CONSISTING OF CHROMIC ACID AND BICHROMATES, SO AS TO IMPROVE THE QUALITY OF SAID MONTAN WAX AND SIMULTANEOUSLY TO FORM A CHROMIC TANNING MASH; SEPARATING THE THUS TREATED MONTAN WAX FROM SAID TANNING MASH; AND SPRAY DRYING THE THUS SEPARATED TANNING MASH SO AS TO TRANSFORM THE SAME INTO A POWDERY DRY SUBSTANCE. 